This research was designed to investigate the processes and mechanisms of genotype-environment interaction in the development and phenotypic expression of behavior. It employs systematic genetic and experiential manipulation of neonatal color preferences in the Coturnix quail, and examines the short and long term effects of such manipulations in the stimulus information processing and phenotypic expression of this behavior. The concept of "behavioral phenotypes" is used in this research in relation to identifiable population values of, and individual variations in, behavioral units, where a behavioral unit is brought about by the administration of an objectively specifiable stimulus information bit and the phenotypic homogeneity of its manifestation in a population is shown by the absence of all but random variation in the resulting response distribution. Our aim is to approach the examination of such behavioral units from two interrelated perspectives: (1) that of the manifest identity of a behavioral unit which differentiates it from another behavioral unit; and (2) that of the developmental identity of a behavioral unit within which different elements and interactions of genetic and experiential factors may result in similar manifestation of the behavioral unit. Research concentrates on neonatal approach preferences in the Coturnix quail because of the unique suitability of these behaviors and fitness of species for behavioral-phenotypic assessment, mass-screening, genetic selection, and study of the interactive genetic and experiential influences in the development and phenotypic expression of behavior. Overall project aim is to identify specific variables in the genotype, in the episodic characteristics of environmental input, in the developmental influences of the environmental input, and in their interactions, in relation to: (1) early processing of stimulus information; (2) lasting modifications in the processing of stimulus information; and (3) mechanisms and morphological mediation of the coding of information pertinent to the phenotypic expression of behavior.